Solid-state energy storage module employing integrated interconnect board

ABSTRACT

An electrochemical energy storage device includes a number of solid-state thin-film electrochemical cells which are selectively interconnected in series or parallel through use of an integrated interconnect board. The interconnect board is typically disposed within a sealed housing which also houses the electrochemical cells, and includes a first contact and a second contact respectively coupled to first and second power terminals of the energy storage device. The interconnect board advantageously provides for selective series or parallel connectivity with the electrochemical cells, irrespective of electrochemical cell position within the housing. Fuses and various electrical and electromechanical devices, such as bypass, equalization, and communication devices for example, may also be mounted to the interconnect board and selectively connected to the electrochemical cells.

GOVERNMENT LICENSE RIGHTS

[0001] The Government of the United States of America has rights in thisinvention pursuant to Cooperative Agreement No. DE-FC02-91CE50336awarded by the U.S. Department of Energy.

FIELD OF THE INVENTION

[0002] This invention relates generally to energy storage devices, andmore particularly, to an apparatus and method for selectivelyinterconnecting a number of independent energy storage cells disposed ina sealed housing.

BACKGROUND OF THE INVENTION

[0003] The demand for new and improved electronic and electromechanicalsystems has placed increased pressure on the manufacturers of energystorage devices to develop battery technologies that provide for highenergy generation in a low-volume package. Conventional battery systems,such as those that utilize lead acid for example, are often unsuitablefor use in high-power, low-weight applications. Other known batterytechnologies may be considered too unstable or hazardous for use inconsumer product applications.

[0004] A number of advanced battery technologies have recently beendeveloped, such as metal hydride (e.g., Ni-MH), lithium-ion, and lithiumpolymer cell technologies, which would appear to provide the requisitelevel of energy production and safety margins for many commercial andconsumer applications. Such advanced battery technologies, however,often exhibit characteristics that provide challenges for themanufacturers of advanced energy storage devices.

[0005] In accordance with a conventional advanced battery design,individual cells are hardwired together and to the positive and negativepower terminals of the battery. Various electronic components which maybe incorporated into the battery design must also be hardwired to thecells. It can be appreciated that such conventional interconnectionapproaches provide for little, if any, flexibility when attempting toalter the series and/or parallel hardwired connections between the cellsand components.

[0006] Moreover, the wiring process typically employed in thefabrication of conventional advanced batteries is generally complicatedand time consuming. An assembly defect of particular concern to themanufacturers of conventional advanced batteries involves unintentionalwiring shorts which develop during the wiring process. Suchmanufacturing defects typically result in a reduction in the performanceand service life of the battery, and often represent a significantsafety concern.

[0007] Other characteristics of advanced battery technologies provideadditional challenges for the designers of advanced energy storagedevices. For example, certain advanced cell structures are subject tocyclical changes in volume as a consequence of variations in the stateof charge of the cell. The total volume of such a cell may vary as muchas five to six percent during charge and discharge cycling. Suchrepetitive changes in the physical size of a cell significantlycomplicates the mechanical housing design, and electrical connectionstrategy. The electrochemical, thermal, and mechanical characteristicsof an advanced battery cell must typically be well understood andappropriately considered when designing an energy storage systemsuitable for use in commercial and consumer devices and systems.

[0008] There is a need in the advanced battery manufacturing industryfor an energy storage device that exhibits high-energy output, and onethat provides for safe and reliable use in a wide range of applications.There exists a further need for an effective interconnection strategywhich provides flexibility and reliability when interconnecting a numberof independent energy storage cells contained within a sealed housing tomeet specified current and voltage ratings. The present inventionfulfills these and other needs.

SUMMARY OF THE INVENTION

[0009] The present invention is directed to an improved electrochemicalenergy storage device. The electrochemical energy storage deviceincludes a number of solid-state, thin-film electrochemical cells whichare selectively interconnected in series or parallel through use of anintegrated interconnect board. The interconnect board is typicallydisposed within a sealed housing or shell which also houses theelectrochemical cells, and includes a first contact and a second contactrespectively coupled to first and second power terminals of the energystorage device. The interconnect board advantageously provides forselective series or parallel connectivity with the electrochemicalcells, irrespective of cell position relative to one another within thehousing. In one embodiment, a sheet of conductive material is processedby employing a known milling, stamping, or chemical etching technique toinclude a connection pattern which provides for flexible and selectiveinterconnecting of individual electrochemical cells within the housing,which may be a hermetically sealed housing. The voltage and currentcharacteristics of the energy storage device are alterable by alteringthe configuration of the connection pattern. Fuses and variouselectrical and electromechanical devices, such as bypass, equalization,and communication devices for example, may also be mounted to theinterconnect board and selectively connected to the electrochemicalcells.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 illustrates an embodiment of a solid-state energy storagedevice which includes a stack of thin-film electrochemical cellsselectively interconnected in a series and/or parallel relationship byuse of an interconnect board;

[0011]FIG. 2 illustrates a surface of an interconnect board having aconnection pattern disposed thereon for providing selective seriesand/or parallel connectivity with a number of electrochemical cells;

[0012]FIG. 3 is another illustration of an interconnect board whichincludes a sheet of conductive material including a connection patternfor selectively connecting a number or electrochemical cells in a seriesor parallel relationship;

[0013]FIG. 4A illustrates another embodiment of an interconnect boardwhich includes a number of components mounted thereon;

[0014]FIG. 4B illustrates yet another embodiment of an integratedinterconnect board;

[0015] FIGS. 5A-5C is an illustration of a component package withinwhich equalizer and bypass devices are integrally incorporated;

[0016]FIG. 6 is an exploded view of an energy storage module includingan interconnect board disposed in a hermetically sealed housing;

[0017] FIGS. 7-9 illustrate an embodiment of a hermetic seal for use ina sealing various types of conduits or feed-throughs that pass into amodule housing;

[0018]FIG. 10 is an illustration of a prismatic electrochemical cellwhich represents one embodiment of an energy storing device which may beused in combination with an integrated interconnect board within asealed module housing in accordance with an embodiment of the presentinvention;

[0019]FIG. 11 is a depiction of various film layers constituting anelectrochemical cell in accordance with the embodiment shown in FIG. 10;and

[0020] FIGS. 12-13 illustrate another embodiment of a hermetic seal foruse in a sealing various types of conduits or feed-throughs that passinto a module housing.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Referring now to the drawings, and more particularly to FIG. 1,there is provided a partial illustration of an embodiment of an energystorage module 35 which utilizes a number of rechargeable solid-statethin-film electrochemical cells for storing electrical energy. Suchrechargeable thin-film electrochemical cells are particularlywell-suited for use in the construction of high-current, high-voltageenergy storage modules and batteries, such as those used to powerelectric vehicles for example.

[0022] As is shown in FIG. 1, the energy storage module 35 includes anumber of individual electrochemical cells 50 which are arranged in astack configuration 46 and situated in a housing 48. Each of theelectrochemical cells 50 includes a pair of electrical leads 52 disposedon opposing edges of the cells 50. It will be appreciated that a genericstack 46 of electrochemical cells 50 may be interconnected in variousparallel and series relationships to achieve desired current and voltageratings. To facilitate selective series or parallel connectivity withinthe stack 46 of electrochemical cells 50, an interconnect board 30 issituated within the housing 48.

[0023] The interconnect board 30 includes a connection pattern orconductivity grid 32 which, when the board 30 is installed within thehousing 48, interconnects the electrochemical cells 50 in accordancewith a pre-established connection configuration. The connection patternor grid 32 is typically affixed or otherwise bonded to a sheet ofinsulating material 34, such as a substantially rigid plastic orlaminate material. A number of electrical and electromechanicalcomponents may also be mounted on the interconnect board 30.

[0024] As is shown in FIG. 1, for example, the interconnect board 30includes a number of fuse packs 40, equalizer and bypass devices 42, andpositive and negative power terminals 38, 36. It is understood that anyor all of the components populating the interconnect board 30 may bemounted on boards or platforms other than the interconnect board 30, andsituated internal to or externally of the module housing 48. In oneembodiment, the interconnect board 30 shown in FIG. 1 and theelectrochemical cells 50 are disposed in a hermetically sealed housing48, as will further be described with respect to FIG. 6.

[0025] As is best illustrated in FIG. 2, the interconnect board 30typically includes a patterned conductive surface 32 whichadvantageously provides for the interconnecting of autonomouselectrochemical cells 50 in accordance with a pre-designed connectionlayout. A significant advantage realized by employing an interconnectboard 30 having a patterned interconnection surface 32 concerns theflexibility by which a desired current and voltage rating may beachieved irrespective of, and without disrupting, the position ofindividual electrochemical cells 50 relative to one another within thehousing 48.

[0026] By way of example, and with particular reference to FIGS. 2-3,the interconnect surface 32 of the interconnect board 30 is selectivelypatterned to achieve a desired cell connection configuration. In thisembodiment, the interconnect surface 32 includes a number ofelectrically isolated connection regions which are pre-designed toelectrically connect with the positive and negative contacts 52 of aparticular number of electrochemical cells 50. In accordance with thisillustrative embodiment, seven isolated connection regions, R₁-R₇, areshown as constituting the patterned interconnect surface 32 of theinterconnect board 30.

[0027] When the interconnect board 30 is installed within the housing 48and adjacent the electrochemical cell stack 46, the electrical contacts52 of a first group of electrochemical cells 50 contact the connectionregion R₁ at a location 54 a. The opposing set of electrical contacts 52of the first group of electrochemical cells 50 electrically contact theconnection region R₂ at a location 54 b. In this configuration, theconnection region R₁ is electrically connected to the negative powerterminal 36.

[0028] A second group of electrochemical cells 50 have their respectiveopposing set of electrical contacts 52 connected to connection regionsR₃ and R₂ at locations 56 a and 56 b, respectively. A third group ofelectrochemical cells 50 have their respective opposing electricalcontacts 52 connected to connection regions R₃ and R₄ at locations 58 aand 58 b, respectively. Subsequent groupings of electrochemical cells 50have their respective opposing electrical contacts 52 connected toconnection regions R₅, R₆, and R₇ in a similar manner. It is noted thatthe connection region R₇ is electrically connected to the positive powerterminal 38.

[0029] It is to be understood that any number of connection regions ofvarying configuration may be provided on the interconnect surface 32 ofthe interconnect board 30. Although each of the connection regions R₁-R₇shown in FIGS. 2-3 electrically communicate with a group ofelectrochemical cells 50, it is understood that a connection region maybe designated to electrically communicate with only a singleelectrochemical cell 50. It can be seen that the first group ofelectrochemical cells 50 are connected in a parallel relationship withrespect to connection regions R₁ and R₂. Similarly, the second group ofelectrochemical cells 50 are connected in parallel with respect toconnection regions R₃ and R₂.

[0030] Having established electrical connectivity with selectedelectrochemical cells 50 at selected isolated connection regions, theconnection regions are then interconnected in a series or parallelmanner through the use of electrical conductors and/or components.Bridging selected isolated connection regions in this manner defines acurrent path the permits current to flow through, for example, thepositive power terminal 38, each of the connection regions R₁-R₇, andthrough the negative power terminal 36.

[0031] In one embodiment, a simple short-circuit bridge or connector maybe used to selectively interconnect the connection regions R₁-R₇ in adesired manner to permit current to flow through the module 30. Inanother embodiment, various electrical or electro-mechanical componentsmay be disposed on the interconnect board 30 which control the flow ofcurrent between isolated connection regions.

[0032] Those skilled in the art will appreciate that an interconnectboard 30 implemented in accordance with the principles of the presentinvention permits flexible and selective connecting of any number ofelectrochemical cells 50 in any desired series or parallel relationship.The interconnect board 30 further permits easy integration of variouscontrol and monitoring devices in series or parallel with respect to theelectrochemical cells. The interconnect surface 32 may be patternedaccording to various pre-designed connection layouts to achieve desiredvoltage and current ratings. The manufacturability of energy storagemodules that satisfy a wide range of power requirements is significantlyimproved by, for example, selecting among a number of interconnectboards 30 having varying interconnect surface configurations, andinstalling a selected interconnect board 30 in a selected modulehousing. A number of different module housing configurations may bedesigned and fabricated to house a particular number of electrochemicalcells based on the energy production requirements of a particularapplication.

[0033] Turning now to FIG. 4A, there is provided a top view illustrationof one embodiment of an integrated interconnect board 30 onto which anumber of control devices are mounted. In either of the embodimentsshown in FIGS. 4A-4B, the bottom of the interconnect board includes aninterconnect surface similar in configuration to that shown in FIGS.2-3. In the configuration shown in FIG. 4A, the energy storage moduleincludes 48 individual electrochemical cells 50 grouped into six cellpacks each comprising eight parallel connected electrochemical cells 50.In the embodiment shown in FIG. 4B, the energy storage module includes64 individual electrochemical cells 50 grouped into eight cell packseach comprising eight parallel connected electrochemical cells 50.

[0034] Associated with each of the six cell packs in FIG. 4A is a fusepack 40 which includes eight fuses (not shown), with one fuse beingconnected in series with one of the eight parallel connectedelectrochemical cells 50 of the cell pack. The fuses within the fusepack 40, when activated, provide for the electrical isolation of adefective cell from the remaining cells of the cell pack. Theinterconnect board 70 shown in FIG. 4B includes eight fuse packs 40 andalso includes temperature sensors 72 which monitor the temperature ofthe interconnect board. A fuse is typically activated, for example, uponthe development of a short-circuit within a particular cell of the cellpack. Various types of suitable fuse devices are disclosed in co-pendingapplication Ser. No. 08/XXX,XXX entitled “In-Situ Short-CircuitProtection System and Method for High-Energy Electrochemical Cells”(Gauthier et al.), the contents of which are incorporated herein byreference.

[0035] A current bypass device may also be affixed to the interconnectboard 30/70 and connected in series with a cell pack which, whenactivated, isolates a cell pack from the series connection and bypassescurrent around the defective cell pack. A number of suitable currentbypass devices are disclosed in co-pending application Ser. No.08/XXX,XXX entitled “Bypass Apparatus and Method for Series ConnectedEnergy Storage Devices” (Rouillard et al.), the contents of which areincorporated herein by reference.

[0036] An equalizer device may further be connected in parallel with acell pack which provides overvoltage protection and balancing of cellpack potentials during charging and discharging operations. A number ofsuitable equalizer devices are disclosed in co-pending application Ser.No. 08/XXX,XXX entitled “Equalizer System and Method for SeriesConnected Energy Storage Devices” (Rouillard et al.), the contents ofwhich are incorporated herein by reference.

[0037] In one embodiment, the equalizer device and bypass device areincorporated into a single integrated. component package, such as theequalizer/bypass module 45 shown in FIG. 4A. Additionally, acommunications device may be connected to each of the cell packs tofacilitate monitoring and controlling of individual cell packs by aninternal or external controller or processor. Also, a temperature sensor47/72 may be mounted on the interconnect board 30/70.

[0038] In FIGS. 5A-5C, there is illustrated an embodiment of anintegrated equalizer/bypass module 45 which, as discussed previously,may be mounted on the interconnect board 30/70. The integratedequalizer/bypass module 45 advantageously provides for a compact housingconfiguration capable of efficiently dissipating heat generated duringequalization and bypass conditions through contact terminals 67, 69affixed to the interconnect board 30/70. The heat conducted through thecontact terminals 67, 69 and to the interconnect board 30/70 may furtherbe conducted to the walls of the housing 48 through thermal conductorsextending from the cells and contacting the housing walls, as will laterbe discussed in greater detail.

[0039] In one embodiment, the integrated equalizer/bypass module 45 hasa total length, L_(T), of 2.75 inches. The housing 65 of theequalizer/bypass module 45 has a length, L_(M), of 2.25 inches. Thetotal width, W_(T), of the equalizer/bypass module 45 is 1.50 inches,while the width of the positive and negative terminals 67, 69 is 1.25inches. The height, H_(T), of the housing 65 is 0.625 inches, and theheight or thickness, H_(c), of the positive and negative terminals 67,69 is 0.05 inches. The ecualizer/bypass module 45 is mounted on theinterconnect board 30/70. The connection surface 32 of the interconnectboard 30/70 includes a patterned copper plate having a thickness of 0.05inches. The thickness of the conductive sheet is required in order topass a relatively high current, and virtually precludes employment ofconventional photo-etched printed circuit board (PCB) techniques.

[0040] It is noted that the heat generated by the equalizer/bypassmodule 45 is typically conducted from the integrated module 45 andinterconnect board 30/70 to the walls of the module casing 48. Inaccordance with this design, the equalizer can pass a current on theorder of 5 amps which results in the generation of approximately 15watts of heat. Those skilled in the art will appreciate that the highcurrent rating of the equalizer provides for relatively high rates ofenergy storage system charging and discharging.

[0041] Returning to FIGS. 2-3, one embodiment of an interconnect board30/70 includes a plastic sheet 34, onto which a number of components aremounted, and a separate sheet of electrically conductive material, whichis patterned to form an interconnect surface 32. The patternedconductive sheet is subsequently affixed to the plastic sheet 34. In oneembodiment, the conductive sheet constitutes a copper sheet having athickness of 0.05 inches and a width and length which varies dependingon the size of the module 35. The copper sheet is machine milled todevelop individual connection regions thereon in accordance with apre-designed pattern layout. It is noted that the pattern layout shouldbe designed to minimize the volume and weight of the copper sheet.

[0042] Following machining of the copper sheet, each of the individualcopper connection regions is cleaned and mounted to the plastic board 34at appropriate locations to facilitate the reconstruction of thepre-designed pattern layout. The plastic board 34 typically has athickness of approximately 0.1 inches, and has a construction similar tocircuit boards commonly used within the electronics industry. The copperconnection regions may be affixed to the plastic board 34 byconventional adhesion or fastening techniques. It is understood thatconductive materials other than copper, such as aluminum for example,may be employed to fabricate the connection regions.

[0043] In an embodiment in which various electronic devices are used tomonitor and control electrical and thermal energy generated within themodule 35, such devices are then mounted to the integrated interconnectboard 30/70. For example, a number of equalizer/bypass modules 45 andcommunication devices 47 are mounted to the interconnect board 30/70.The equalizer/bypass modules 45 and positive and negative powerterminals 38, 36 may be welded to the interconnect board 30/70, such asby employing a known ultrasonic welding technique. Alternatively, an airflow brazing or spot welding technique may be employed to mount theequalizer/bypass module 45 and terminals 36, 38 to the interconnectboard. 30/70.

[0044] In addition to mounting the equalizer/bypass modules 45 andterminals 36, 38, the fuse packs 40 may be mounted on one or both sidesof the interconnect board 30/70, depending on the cell configuration andthe need to minimize the weight and volume of the interconnect surface32. One side 51 of the fuse packs 40 is ultrasonically welded to theinterconnect board 30/70. It is noted that the use of ultrasonic weldingto mount various components to the interconnect board 30/70 results inthe overall reduction in heat generated during the welding procedure incomparison to other known welding techniques. However, air flow brazing,soldering, or spot welding techniques may be employed in combinationwith well-designed heat sinks.

[0045] Finally, the interconnect board 30/70 is mounted on the stack 46of electrochemical cells 50. Each of the cell terminals 52 is connectedto the interconnect board 30/70, which may be performed by ultrasonicwelding, soldering, or spot welding. Table 1 below provides various dataassociated with the use of an interconnect board 30/70, such as thatshown in FIGS. 4A-4B, for interconnecting a number of individualelectrochemical cells 50 and various electronic devices encased in asealed module housing 48. The data tabulated in Table 1 demonstratesthat a total resistance of approximately 8 micro-ohms and a total weightof 7 to 14 grams may be realized by employing an integrated interconnectboard 30/70 of the type illustrated herein for use in a power systemcapable of passing on the order of 400 A of peak current with less thanapproximately 4 mV of voltage drop across the power terminals and apower loss on the order of 1 watt. TABLE 1 Volume Resistance Volt.Thickness cube Weight microohm drop Power Energy Material Mils metergrams @ 80° C. mVolts Watts Joules Copper 50 1.6E−06  14.41 8.39 3.361.34 40.29 Aluminum 80 2.58E−06 6.94 8.64 3.46 1.38 41.48

[0046] In FIG. 6, there is illustrated an exploded view of a powergenerating module 100 that includes an inner shell 101 which contains astack 105 of electrochemical cells 121 and various electronic boards,including an interconnect board 104 of the type previously discussed. Aninner shell cover 108 incorporates a hermetic seal 115, such as thatdescribed below with respect to FIGS. 7-9, that seals variousfeed-throughs provided in the inner shell cover 108.

[0047] In accordance with one embodiment, the module 100 includes astack 105 of electrochemical cells 121 which are interconnected throughuse of the interconnect board 104. The stack 105 of electrochemicalcells 121 are segregated into six cell packs 125, all of which arebanded together by use of two bands 127 and two opposing end plates 129.The 48 electrochemical cells 121 are subjected to a continuouscompressive force generated by use of the bands 127/end plates 129 and afoam or spring-type element disposed within or adjacent each of thecells 121. Each electrochemical cell 121 includes a thermal conductorwhich is spot welded or otherwise attached respectively to one or bothof the positive and negative cell contacts.

[0048] The positive and negative contacts of the thermal conductorscarry current from the cells 121 to the interconnect board 104. Thethermal conductors also conduct heat from the cells to a metallic innershell 101 which serves as a heat sink. The thermal conductors include aspring portion which deforms when the cell 121 is inserted into theinner shell 101, accommodating tolerances in cell length and changes inseparation distances between the cells 121 and the inner shell 101.

[0049] The inner shell 101 has a thickness of approximately 1 mm and isfabricated from deep drawn aluminum or stainless steel. The interiorsides of the inner aluminum shell 101 include an anodized coating havinga thickness of approximately 0.64 mm. The anodized surface of the innershell 101 provides electrical insulation between adjacent cells 121, yetprovides for the efficient transfer of heat generated from the cells 121through contact with the resilient cell conductors. In the case of astainless steel inner shell 101, thin plastic or mica sheet may besituated between the cells 121 and the inner shell walls.

[0050] The interconnect board 104 is situated above the cell stack 105and includes control circuitry for each of the respective six cell packs125 constituting the cell stack 105. Each cell pack control unit 113includes a short circuit protection device such as a fuse pack 107, abypass device, and an equalizer circuit which control the operation ofthe cell pack 125 while charging and discharging. Accordingly, each ofthe cell packs 125 is monitored and controlled by a respective cell packcontrol unit 113. A control board 106, situated above the interconnectboard 104, includes a processor that monitors and controls each of thesix cell pack control units 113. As such, the control board 106 providesfor cell pack and module level monitoring and control during chargingand discharging operations.

[0051] A pair of quick connectors 117 pass through corresponding holesprovided in an inner shell cover 108 and serve as the main powerterminals of the module 100. The quick connectors 117 are hermeticallysealed to the inner shell cover 108 using a sealing apparatus 115. Whenan outer shell cover 112 is positioned onto the inner shell cover 108,the quick connectors 117 are received into mating sockets 119 mounted onthe interconnect board 104. Communication connectors 111, which passthrough the inner shell cover 108 and are similarly hermetically sealedthereto, provide external access to the control board 106 and otherelectronic boards of the module 100.

[0052] A hermetic seal is provided between the inner shell 101 and innershell cover 108 by welding the inner shell cover 108 to the top of theinner shell 101. The hermetically sealed inner shell 101 is theninserted into an outer shell 102. The outer shell 102 may be fabricatedfrom glass filled polypropylene through use of an injection moldingprocess, and has a thickness of approximately 2 mm. The outer shell 102includes ribs on three sides of the inner surface which form flowchannels when the inner shell 101 is installed in the outer shell 102for the purpose of transporting a heat transfer fluid therebetween. Theouter shell cover 112 may be vibration welded to the top of the outershell 102. Fluid connectors 120 are disposed on the outer shell cover112 and provide for the flow of heat transfer fluid into and out of themodule 100.

[0053] Referring to FIGS. 7-9, there is illustrated a hermetic sealapparatus which may be employed to provide hermetic sealing between aconduit, such as an electrical feed-through provided in a housing coverof a power generating module, and a passage in the housing. Power andcommunication lines, for example, may be passed through the conduit toprovide external connectivity with power and electronic componentscontained within the hermetic environment of an encased power generatingmodule.

[0054] The hermetic seal 220 shown in FIGS. 7-9 includes a first sealbody 222 having a central passage which is in general alignment with ahole provided through a substantially planar plate 221, such as a coverof a power generating module housing. A second seal body 224 of the seal220 also includes a central passage which is in general alignment withthe hole of the cover 221 and the central passage of the first seal body222. The first seal body 222 is disposed on an upper surface of thecover 221, and the second seal body 224 is disposed on a lower surfaceof the cover 221.

[0055] In one embodiment, the first seal body 221 includes a collar 233which extends through the hole of the cover 221 and bears against aninner surface 239 of the hole. The collar 233 includes a tapered innersurface 238 which tapers away from the central passage of the first sealbody 222. The second seal body 224 includes a groove 235 having an innertapered surface 240 which tapers toward the central passage of thesecond seal body 224.

[0056] As is best illustrated in the pre-sealed and post-sealeddepictions provided in FIGS. 8 and 9, respectively, the collar 233 ofthe first seal body 222 is received by the groove 235 provided in thesecond seal body 224 such that the tapered surfaces 238, 240 of thefirst and second seal bodies 222, 224 slidably engage one another as thecollar 233 is forced into the groove 235. Engagement of the opposingtapered surfaces 238, 240 of the first and second seal bodies 222, 224in a fully installed configuration forces a portion 237 of the outersurface of the collar 233 to cold flow against the inner surface 239 ofthe hole provided in the cover 221. Those skilled in the art willappreciate that cold flowing one material against another material formsan extremely tight seal between the two materials. As such, a hermeticseal is provided between the inner surface 239 of the hole and thecollar 233 through slidable engagement between the collar 233 of thefirst seal body and the groove 235 provided in the second seal. body224.

[0057] As is further shown in FIGS. 7-9, a conduit 226, having a firstend 223 and an opposing second end 227, passes through the hole in thecover 221 and the central passages of the first and second seal bodies222, 224. The conduit 226 includes a central passage through whichelectrical and communication lines may pass into the internal hermeticenvironment of a housing to which the cover 221 is mounted. The conduit226 includes a flange 225 which extends outwardly from the first end 223of the conduit 226 and contacts a surface of the first seal body 222.The conduit 226 has a diameter which is substantially equivalent to thediameter of the central passages of the first and second seal bodies222, 224 such that an outer surface 242 of the conduit 226 forms atight, smooth fit with the inner diameter surfaces of the first andsecond seal body central passages.

[0058] A portion of the second end 227 of the conduit 226 is threaded sothat a nut 234 may be secured thereon. The seal 220 also includes athrust washer 228 that abuts a lower surface of the second seal body224. A wave washer 230 is disposed between the thrust washer 228 and asecond thrust washer 232. A nut 234, in abutment with the second thrustwasher 232, exerts an axially directed compressive force on the elementsof the hermetic seal 220 as the nut 234 is tightened on the threadedsecond end 227 of the conduit 226.

[0059] As is best seen in FIG. 9, a compressive force, F_(c), producedby the tightened nut 234 causes the wave washer 230 to compress which,in turn, forces the inwardly tapered inner surface 240 of the secondseal body 224 into slidable engagement with the outwardly tapered innersurface 238 of the first seal body 222. Application of the compressiveforce, F_(c), drives the inner diameter surface 241 of the second sealbody 224 inwardly against the outer surface 242 of the conduit 226.Slidable engagement between the two tapered surfaces 238, 240 alsodrives a portion 237 of the collar 233 into tight engagement with theinner surface 239 of the hole provided in the cover 221. Aftertightening the nut 234 to generate an appropriate level of compressiveforce, F_(c), the wave washer 230 continues to apply the compressiveforce, F_(c), so as to maintain the integrity of the hermetic seal 220over the service life of the seal. It is understood that the compressiveforce, F_(c), may be produced by a fastener apparatus other than thatshown in FIG. 7, such as by use of a spring-loaded metal keeper. Otherretention devices which are capable of maintaining a continuouscompressive force, F_(c), may also be employed.

[0060] In one embodiment, the cover 221 is constructed from a metallicmaterial, such as aluminum or stainless steel, and the first and secondseal bodies 222, 224 are fabricated from a plastic material, such aspolypropylene plastic. The conduit 226 may be fabricated from a metallicor a plastic material. It is noted that gaps 246, 247 may be provided inthe first and second seal bodies 222, 224, respectively, to accommodatepositional shifting between the first and second seal bodies 222, 224occurring from forced engagement of the two tapered surfaces 238, 240.Also, a notch 251 may be provided in the first seal body 222 tofacilitate movement of the collar 233 in a direction toward the innersurface of the hole of the cover 221 in response to slidable engagementbetween the two tapered surfaces 238, 240.

[0061] An alternative hermetic sealing apparatus or feed-through isshown in FIGS. 12-13. In accordance with this embodiment, hermeticsealing is provided primarily by an o-ring 464 which is compressedbetween a flanged conductor or terminal 462 and a wall or cover 468 ofthe module housing. A phenolic support 466 keeps the flanged conductor462 at a constant distance from the cover 468, thus creating a cavitywhose dimensions are stable over time. This arrangement prevents flowingof the o-ring material with time and high temperature.

[0062] A polypropylene ring 470 and sleeve 472 electrically insulate thebottom portion of the feed-through from the cover 468. In contrast tothe phenolic ring material, polypropylene maintains its high dielectricstrength even after being subjected to arcing. It is noted that arcingtypically occurs, if at all, between the o-ring 464 and thepolypropylene sleeve 472. Another advantage of using polypropylenematerial for the ring 470 and sleeve 472 material is that it provides acoefficient of friction that is sufficient to prevent the assembly fromturning when subjected to the torque generated when wires are connectedto the flanged conductors 462. The Belleville spring 474 is flattenedwhen the feed-through is crimped. The Belleville spring 474 ensures thatthe assembly will be kept under pressure even if the polypropylene flowsover time. The metal washer 476 helps to distribute pressure evenlyacross the surface of the polypropylene ring 470.

[0063] In general, the above-described hermetic sealing apparatusesexhibit a high dielectric strength between the housing cover or wall anda power conductor passing through the cover. Power terminal voltages onthe order of 2,000 V can be accommodated without occurrences of arcing.Tight sealing (e.g., 10⁻⁸⁻ cc-atm/sec) is maintained even when subjectedto mechanical stresses. The hermetic seals also exhibit good torqueresistance and good overall mechanical resistance.

[0064] In accordance with one embodiment of the present invention, thepower sources shown in FIG. 6 may constitute solid-state, thin-filmcells of the type shown in FIGS. 10-11. Such thin-film electrochemicalcells are particularly well-suited for use in the construction ofhigh-current, high-voltage power generating modules and batteries, suchas those used to power electric vehicles for example. In FIG. 10, thereis shown an embodiment of a prismatic electrochemical cell 300 whichincludes an anode contact 301 and a cathode current collector contact303 formed respectively along opposing edges of the electrochemical cell300.

[0065] A thermal conductor 302 is spot welded or otherwise attached toeach of the anode and cathode contacts 301, 303, respectively. A thermalconductor 302 is typically disposed along the length of the anodecontact 301 and the cathode current collector contact 303, and typicallyincludes an electrical connection lead 304 for conducting current intoand out of the electrochemical cell 300, the current being collected andconducted along the anode and cathode contacts 301, 303. The thermalconductor 302 may be fashioned from copper and have a substantiallyC-shaped, double C-shaped, Z-shaped, V-shaped, S-shaped or O-shapedcross-section.

[0066] In this embodiment, the electrochemical cell 300 is fabricated tohave a length L of approximately 135 mm, a height H of approximately 149mm, and a width W_(ec) of approximately 5.4 mm or approximately 5.86 mmwhen including a foam core element. The width W_(c) of the cathodecurrent collector contact 303 and the anode contact 301 is approximately3.9 mm, respectively. Such a cell 300 typically exhibits a nominalenergy rating of approximately 36.5 Wh, a peak power rating of 87.0 W at80 percent depth of discharge (DOD), and a cell capacity of 14.4 Ah atfull charge. Each of the electrochemical cells 300 has a nominaloperating voltage ranging between approximately 2.0 V and 3.1 V.

[0067] The electrochemical cell shown in FIG. 10 may have a constructionsimilar to that illustrated in FIG. 11. In this embodiment, anelectrochemical cell 380 is shown as having a flat wound prismaticconfiguration which incorporates a solid polymer electrolyte 386constituting an ion transporting membrane, a lithium metal anode 384, avanadium oxide cathode 388, and a central current collector 390. Thesefilm elements are fabricated to form a thin-film laminated prismaticstructure, which may also include an insulation film, such aspolypropylene film.

[0068] A known sputtering metallization process is employed to formcurrent collector contacts along the edges 385, 383 of the anode andcathode current collector films 384, 390, respectively. It is noted thatthe metal-sprayed contacts provide for superior current collection alongthe length of the anode and cathode film edges 385, 383, and demonstrategood electrical contact and heat transfer characteristics. A spring-likethermal conductor or bus bar, such as the thermal conductor 302 shown inFIG. 10, is then spot-welded or otherwise attached to the metal-sprayedcontact. The electrochemical cells illustrated in the Figures may befabricated in accordance with the methodologies disclosed in U.S. Pat.Nos. 5,423,110, 5,415,954, and 4,897,917.

[0069] It will, of course, be understood that modifications andadditions can be made to the various embodiments discussed hereinabovewithout departing from the scope or spirit of the present invention. Byway of example, the principles of the present invention may be employedfor use with battery technologies other than those exploiting lithiumpolymer electrolytes, such as those employing nickel metal hydride(Ni-MH), lithium-ion, (Li-Ion), and other high-energy batterytechnologies. Accordingly, the scope of the present invention should notbe limited by the particular embodiments discussed above, but should bedefined only by the claims set forth below and equivalents thereof.

What we claim is:
 1. A method of connecting a plurality of thin-filmelectrochemical cells disposed in a hermetically sealed housing of anenergy storing module to positive and negative terminals passing throughthe housing, the method comprising: forming a connection pattern on anelectrically conductive surface of an interconnect board; installing theinterconnect board in the housing; connecting positive and negativecontacts of the interconnect board to the positive and negative housingterminals; connecting leads of the electrochemical cells to theconnection pattern; and hermetically sealing the housing.
 2. The methodof claim 1, wherein hermetically sealing the module housing compriseshermetically sealing the positive and negative terminals passing throughthe housing.
 3. The method of claim 1, wherein connecting the leadsincludes ultrasonically welding the leads of the electrochemical cellsto the connection pattern.
 4. The method of claim 1, wherein voltage andcurrent characteristics of the energy storing module are alterable byaltering the connection pattern formed on the electrically conductivesurface of the interconnect board.
 5. The method of claim 1, whereinforming the connection pattern comprises processing a metallic sheetmaterial to include one of a machine milled connection pattern, astamped connection pattern, or a chemically etched connection pattern.6. The method of claim 1, wherein forming the connection pattern furthercomprises: forming a plurality of connection regions each beingconnected to particular ones of the plurality of electrochemical cells;and electrically coupling the connection regions together and to thepositive and negative contacts of the interconnect board.
 7. The methodof claim 6, wherein electrically coupling the connection regionstogether comprises electrically coupling the connection regions togetherusing a current bypass device.